1. Field of the Invention
The present embodiment relates to a substrate carrying mechanism for carrying a substrate, a substrate carrying method, and a recording medium storing a program including a set of instructions to be executed to accomplish the substrate carrying method.
2. Description of Related Art
A semiconductor device fabricating system for fabricating semiconductor devices or LCD panels (liquid crystal display panels) is provided with processing modules that process substrates (hereinafter, referred to also as “wafers”). A substrate carrying mechanism carries substrates sequentially to the processing modules to subject the substrates to predetermined processes. The substrate carrying mechanism has, for example, a base, and a substrate holding fork capable of being advanced and being retracted along the base, of turning about a vertical axis and of moving vertically.
Substrate carrying mechanisms mentioned in, for example, Patent documents 1 and 2 are provided with sensors for determining whether or not a substrate received from the processing module is held at a correct position on the holding fork.
A semiconductor device fabricating system disclosed in Patent document 1 is provided with a substrate carrying mechanism including a carrying robot having an arm, i.e., holding fork, for holding a substrate. This semiconductor device fabricating system determines a positional error of a substrate in each of a plurality of units of the semiconductor device fabricating system from the position of the substrate on the arm (holding fork). The semiconductor device fabricating system is provided with correcting means for correcting the positional error of the substrate by adjusting a carrying distance for which the substrate is carried between the units. The positional error of the substrate is determined by measuring positions of a plurality of parts of the edge of the substrate.
The substrate carrying mechanism disclosed in Patent document 2 has a carrying arm unit, a pick-up unit (holding fork), a position measuring unit for measuring the position of a substrate, a center-position calculating unit, a displacement calculating unit, and an arm control unit. The position measuring unit mentioned in Patent document 2 is mounted on the pick-up unit (holding fork) to measure the position of a substrate held by the pick-up unit. The center-position calculating unit calculates the position of the center of the substrate by using data provided by the position measuring unit. The displacement calculating unit calculates a positional error of the center of the substrate with respect to a predetermined reference position. The arm control unit controls the movement of the carrying arm unit such that the positional error of the center of the substrate is corrected while the substrate held by the pick-up unit (holding fork) is being carried to a desired position.